Slide member

ABSTRACT

A slide member includes a surface layer having a slide surface for sliding on a mating member, wherein the surface layer has metal crystals belonging to a cubic system with a crystal plane of high atomic density directed toward the slide surface and form the slide surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a slide member, and more particularly, to aslide member comprising a surface layer having a slide surface for amating member.

2. Description of the Prior Art

There are conventionally known as a slide member of such type: a pistonfor an internal combustion engine, which has a base material of an Alalloy provided with grooves for receiving piston rings, wherein theinner surface of the groove is provided with a surface layer comprisedof a metal plated layer so as to improve the wear resistance of thegroove; a piston for an internal combustion engine, which has a basemateral of an Al alloy provided with a surface layer comprised of ametal plated layer on an outer peripheral surface of its skirt portionso as to improve the wear resistance of the skirt portion; a slidebearing with a surface layer comprised of a Pb alloy; and similarconstructions.

However under existing circumstances where it has been desired toincrease speed and output of an engine, the surface layer of theabove-described pistons suffers from a poor wear resistance due to a lowhardness and also from a low strength.

The above-described slide bearing is applicable to a journal portion ofa crankshaft, an enlarged end of a connecting rod or the like in aninternal combustion engine. However under the above-describedcircumstances, the surface layers of the prior art slide bearings sufferfrom an insufficient oil retention property and a poor seizureresistance due to an inferior initial conformability.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a slide member ofthe type described above, which has a surface layer formed to have ahigh hardness by specifying the metal crystal structure of the surfacelayer, thereby improving the wear resistance and the strength of thesurface layer.

It is another object of the present invention to provide a slide memberof the type described above, wherein the sufficient oil retentionproperty is achieved on the surface layer and the initial conformabilityof the surface layer can be improved by specifying the metal crystalstructure of the surface layer, thereby providing an increased seizureresistance of the surface layer.

To achieve the above objects, according to the present invention, thereis provided a slide member, comprising a surface layer having a slidesurface for a mating member, wherein the surface layer has a metalcrystal structure belonging to a cubic system with crystal planes ofmetal crystals of high atomic density being directed so as to form theslide surface.

The crystal planes are planes of the metal crystal and the percent areaA of the close-packed planes in the slide surface is set in the range ofA≧30%. In addition, the metal crystal has a body-centered cubicstructure, and the crystal plane is a secondary slip plane. The percentarea B of the secondary slip planes in the slide surface is set in therange of B≧50%.

By providing the metal crystal structure of the surface layer asdescribed above, a high hardness of the surface layer can be achieved,thereby providing the slide member with an improved wear resistance andan improved strength.

In addition, according to the present invention, there is provided aslide member comprising a surface layer having a slide surface for amating member, wherein the surface layer is formed of an aggregate ofcrystals of a Pb alloy, the aggregate including first oriented crystalswith planes (h00) by Miller indices thereof directed toward the slidesurface and second oriented crystals with planes (111) and (222) byMiller indices thereof directed toward the slide surface. Underapplication of an X-ray diffractometry to the surface layer, where anintegrated strength of the first oriented crystals is represented byI(a) and an integrated strength of the second oriented crystals isrepresented by I(b), the following relation is established:0.6≦I(a)/ΣI(ab)≦1.0 wherein ΣI(ab)=I(a)+I(b) , and I(b)=0 is included.

By specifying the metal crystal structure of the surface layer asdescribed above, the slide member can have an increased seizureresistance of the surface layer.

The above and other objects, features and advantages of the presentinvention will become apparent from a consideration of the followingdescription of the preferred embodiments, taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-11 show a first embodiment of the invention, wherein

FIG. 1 is a side view of a piston;

FIG. 2 is an enlarged sectional view taken along a line 2--2 in FIG. 1;

FIG. 3A is a perspective view illustrating a close-packed plane of aface-centered cubic structure;

FIG. 3B is a perspective view illustrating a close-packed plane of abody-centered cubic structure;

FIG. 4A is an illustration for explaining an inclination of theclose-packed plane of the face-centered cubic structure;

FIG. 4B is an illustration for explaining an inclination of theclose-packed plane of the body-centered cubic structure;

FIG. 5 is an X-ray diffraction pattern for Fe crystals in a surfacelayer;

FIG. 6 is a photomicrograph showing a structure of the Fe crystals in aslide surface;

FIG. 7 is an X-ray diffraction pattern for Cr crystals in a surfacelayer;

FIG. 8 is an X-ray diffraction pattern for Ni crystals in a surfacelayer;

FIG. 9 is a photomicrograph showing a structure of the Ni crystals in aslide surface;

FIG. 10 is a graph illustrating the relationship between the percentarea A of a close-packed plane in a slide surface and the hardness of asurface layer; and

FIG. 11 is a graph illustrating the relationship between the percentarea A of a close-packed plane in a slide surface and the amount of wearof a surface layer.

FIGS. 12-22 show a second embodiment of the invention, wherein

FIG. 12 is a side view of a piston;

FIG. 13 is an enlarged sectional view taken along a line 13--13 in FIG.12;

FIG. 14 is a perspective view illustrating a secondary slip plane of abody-centered cubic structure;

FIG. 15 is an illustration for explaining an inclination of a secondaryslip plane of a body-centered cubic structure;

FIG. 16 is an X-ray diffraction pattern for Fe crystals in a surfacelayer;

FIG. 17 is a photomicrograph showing a structure of the Fe crystals in aslide surface;

FIG. 18A is a graph illustrating the hardness of surface layersaccording to the embodiment and a comparative example;

FIG. 18B is a graph illustrating the amount of wear of surface layersaccording to the embodiment and the comparative example;

FIG. 19A is a graph illustrating the density of cracks in surface layersaccording to the embodiment, the comparative example and a referentialexample;

FIG. 19B is a graph illustrating the strength of surface layersaccording to the embodiment and the comparative example;

FIG. 20 is a plan view of a test piece;

FIG. 21 is an X-ray diffraction pattern for Fe crystals in a surfacelayer in another form of the embodiment; and

FIG. 22 is a photomicrograph showing a structure of the Fe crystals in aslide surface in a further form of the embodiment.

FIGS. 23-33 show a third embodiment of the invention, wherein

FIG. 23 is an exploded plan view of a slide bearing;

FIG. 24 is an enlarged sectional view taken along a line 24-24 in FIG.23;

FIG. 25 is a schematic view of an essential portion of the slidesurface;

FIG. 26 is a schematic longitudinal sectional view of an essentialportion of the surface layer;

FIG. 27 is an illustration for explaining the measurement of theinclination angle of a first oriented crystal;

FIG. 28 is an X-ray diffraction pattern for Pb alloy crystals in thesurface layer;

FIG. 29 is a photomicrograph showing a structure of the Pb alloycrystals in the slide surface;

FIG. 30 is a photomicrograph showing a structure of Pb alloy crystals,taken through a longitudinal section of the surface layer;

FIG. 31 is a photomicrograph showing a structure of Pb alloy crystals inanother form of the slide surface;

FIG. 32 is a graph illustrating the relationship between the presencerate R₁ of first oriented crystals and the surface pressure of thesurface layer when seizure occurs; and

FIG. 33 is a graph illustrating the relationship between the presencerate R₂ of third oriented crystals and the surface pressure of thesurface layer when seizure occurs.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 to 11 show a first embodiment of the present invention.

Referring to FIGS. 1 and 2, a piston 1, serving as a slide member for aninternal combustion engine, has a base material 2 of an Al alloy, whichhas grooves 3 for receiving piston rings 5. A surface layer 4 isprovided on an inner surfaces of each groove 3 of the base material 2.The surface layer 4 has a slide surface 4a in contact with the pistonring 5 serving as a mating member.

The surface layer 4 is formed by an electroplating process and comprisesan aggregate of metal crystals belonging to a cubic system. Aface-centered cubic structure (which is called an fcc structurehereinafter) and a body-centered cubic structure (which is called a bccstructure hereinafter) are included in the cubic system.

Metals having a fcc structure are listed, for example, as Pb, Ni, Cu,Al, Ag, Au and the like. Metals having a bcc structure are listed, forexample, such as Fe, Cr, Mo, W, Ta, Zr, Nb, V and the like.

As shown in FIG. 3A, a close-packed plane a₁ in the fcc structure S₁ isa (111) plane (by Miller indices) including six atoms. A close-packedplane al in the bcc structure S₂ is a (110) plane (by Miller indices)including five atoms, as shown in FIG. 3B.

Predetermined crystals of the metal crystals have their close-packedplanes a₁ as the crystal surface of a high atomic density directed so asto define the slide surface 4a. The percent area A of the close-packedplanes a₁ in the slide surface 4a is set in the range of A≧30%.

Since the close-packed plane a₁ is higher in atomic density than theother crystal surfaces, a high hardness can be achieved in the slidesurface 4a, namely the surface layer 4 by providing the percent area Aas described above. This leads to an improvement in the wear resistance.When the percent area A is less than 30%, the hardness in the surfacelayer 4 deteriorates.

An inclination of the close-packed plane a₁ with respect to a phantomplane C extending along the slide surface 4a affects the wear resistanceof the surface layer 4.

The inclination angle Θ of the close-packed plane a₁ of the fccstructure S₁ with respect to a phantom plane C is set in the range of0°≦Θ≦20° as shown in FIG. 4A. The inclination angle Θ of theclose-packed plane a₁ of the bcc structure S₂ with respect to a phantomplane C is set in the range of 0°≦Θ≦20° as shown in FIG. 4B. When theinclination angle Θ becomes larger than 20°, the wear resistance of thesurface layer deteriorates.

Some preferred examples will be described below.

The inner surface of the annular recess 3 in the base material 2 of anAl alloy was subjected to an electroplating process so as to form thesurface layer 4 comprised of an aggregate of Fe crystals.

The conditions for the electroplating process were as follows: a platingbath of ferrous sulfate was used; the pH of the plating bath was 3 orless (constant); an additive of carbamide, boric acid, saccharin andammonium sulfate was used; the temperature of the plating bath was 50°C.; and the cathode current density was 8 A/dm².

FIG. 5 is a X-ray diffraction pattern diagram for Fe crystals in thesurface layer 4, wherein a peak b₁ indicates a plane (110) as theclose-packed plane a₁, and a peak b₂ indicates a plane (211). It can beseen from FIG. 5 that there exist in the surface layer 4 Fe crystalswhich are oriented so that their close-packed planes a₁ lie in a planeparallel to the phantom plane C extending along the slide surface 4a.

In this case, the greater the height of the peak b₁ and thus the theintegrated strength of peak b₁, the greater the degree of orientation ofplane a₁ of the Fe crystals is with respect to phantom plane C. Thisresults in an increased percent area A occupied by the close-packedplanes a₁ in the slide surface 4a. The degree of orientation iscontrolled by varying the conditions for the electroplating process. InFIG. 5, the percent area A of the closepacked planes a₁ in the slidesurface 4a is equal to 30% (A=30%). The Fe crystal structure of the Fein the slide surface 4a is shown by an electron photomicrograph (5,000×magnification) in FIG. 6.

Two base materials 2 were prepared. The inner surface of the groove 3 ofone of the base materials 2 was subjected to an electroplating processso as to form a surface layer 4 comprised of Cr crystals. A surfacelayer comprised of Ni crystals was formed on the inner surface of thegroove 3 of the other of the base materials 2 in the same manner.

FIG. 7 is a X-ray diffraction pattern diagram for the Cr crystals in thesurface layer 4, wherein a peak b, indicates a plane (211). In thiscase, the percent area A of the close-packed plane (110) as theclose-packed plane a₁, and a peak b₂ indicates planes a₁ in the slidesurface 4a is equal to 65%.

FIG. 8 is a X-ray diffraction pattern diagram for the Ni crystals in thesurface layer 4, wherein a peak b₃ indicates a plane (111) as theclose-packed plane a₁, and a peak b₄ indicates a plane (200). In thiscase, the percent area A of the close-packed planes a₁ in the slidesurface 4a is equal to 65%. The Ni crystal structure in the slidesurface 4a is shown by an electron photomicrograph (5,000×magnification) in FIG. 9.

In the respective surface layers 4 comprised of the Fe crystals, the Crcrystals and the Ni crystals, the inclination angle Θ of theclose-packed plane a₁ were in the range of 0°≦Θ≦20°.

FIG. 10 illustrates results of a hardness test for the respectivesurface layers 4. A measurement using micro Vickers hardness wasconducted with a hypermicrophotometer under a load of 5 g. In FIG. 10, aline c₁ indicates the result of the surface layer 4 comprised of the Fecrystals, a line c₁ indicates the result of the surface layer 4comprised of the Cr crystals, and a line c₃ indicates the result of thesurface layer 4 comprised of the Ni crystals.

As is apparent from FIG. 10, the hardness of the surface layer 4 can beimproved by specifying the percent area A of the close-packed planes a₁in the range of 30% or more.

FIG. 11 illustrates results of a wear test for the respective surfacelayers 4. A measurement of the amount of wear was conducted with atip-on-disk testing machine. The test conditions were as follows: theload on the tip was set at 10 kgf; the material of the disk was anitrided carbon steel material (S48C material); the speed of revolutionsof the disk was set at 0.5 m/sec; and the sliding distance was 1000 m.Lines c₁ to c₃ in FIG. 11 correspond to the lines c₁ to c₃ in FIG. 10,respectively.

As is apparent from FIG. 11, the wear resistance of the surface layer 4can be improved by specifying the percent area A of the closepackedplanes a₁ in the range of 30% or more.

The improved technology of this invention found in the above-describedfirst embodiment is not limited to the above-described piston, but alsois applicable to other slide members such as a pulley provided with asurface layer having metal crystals such as of Ni, Fe and Cr on a beltgroove, a rocker arm for an internal combustion engine provided with asurface layer having metal crystals such as of Cr on a slipper, and acam shaft for an internal combustion engine provided with a surfacelayer having metal crystals such as of Cr on a journal portion.

FIGS. 12 to 22 illustrate a second embodiment of the present invention.

Referring to FIGS. 12 and 13, a piston 1 for an internal combustionengine, serving as a slide member, has a base material 2 of an Al alloy.A surface layer 4 is provided on an outer surface of a skirt portion 6of the piston 1 the base material 2. The surface layer 4 has a slidesurface 4a in contact with an inner surface 7 of a cylinder bore (amating member).

The surface layer 4 is formed by an electroplating process and comprisesan aggregate of metal crystals having a bcc structure. The metalcrystals having a bcc structure are comprised, for example, of crystalssuch as of Fe, Cr, Mo, W, Ta, Zr, Nb, V and the like.

As shown in FIG. 14, a primary slip plane and thus close-packed plane a₁in the bcc structure S₂ is a plane (110). The orientation d of slip isrepresented by the direction <111>. When a secondary slip plane isdefined here as a crystal surface which includes the orientation of slipof the metal crystals and is highest in atomic density except theclose-packed plane al, then the secondary slip plane a₂ corresponds to aplane (211) or a plane (123). In the illustration, a plane (211) ispresented as the secondary slip plane a₂.

Predetermined crystals included in metal crystals have their secondaryslip planes a₂ as a crystal plane of high atomic density directed towardand defining the slide surface 4a. The percent area B of the secondaryslip planes a₂ in the slide surface 4a is set in the range of B≧50%.

If the orientation property is applied to the metal crystals in theabove manner, a high hardness can be achieved in the surface layer 4,thereby improving the wear resistance of the surface layer 4.

In addition, the density of cracks in the surface layer 4 is reduced andhence, in cooperation with the afore-mentioned high hardness property,the strength of the surface layer 4 can be improved. In the metalcrystals, the orientation degree of the plane (211) as the secondaryslip plane a₂ and the orientation degree of the plane (110) as theclose-packed plane a₁ have a relationship such that the orientationdegree of one of the planes decreases as the orientation degree of theother of the planes increases. In this case, as the orientation degreeof the plane (110) increases the density of cracks in the surface layer4 tends to increase. Therefore it is very advantageous to increase theorientation degree of the plane (211) in order to improve the strengthof the surface layer 4. When the percent area B becomes less than 50%,the density of cracks in the surface layer 4 becomes higher, therebyreducing the strength of the surface layer 4.

The inclination of the secondary slip plane a₂ with respect to a phantomplane C extending along the slide surface 4a affects the wear resistanceof the surface layer 4. For that reason, the inclination angle e of thesecondary slip plane a₂ in the bcc structure S₂ with respect to thephantom plane C is set in the range of 0°≦Θ≦30° as shown in FIG. 15.When the inclination angle Θ exceeds 30°, the wear resistance of thesurface layer 4 deteriorates.

Samples preferred examples will now be described.

The outer surface of a skirt portion 6 in a base material 2 of an Alalloy was subjected to an electroplating process so as to form a surfacelayer 4 comprised of an aggregate of Fe crystals.

The conditions for the electroplating process were as follows: a platingbath of ferrous sulfate was used; the pH of the plating bath was 3 orless (constant); an additive of carbamide, boric acid, saccharin andammonium sulfate was used; the temperature of the plating bath was 60°C.; and the cathode current density was 8 A/dm².

FIG. 16 is a X-ray diffraction pattern diagram for the Fe crystals inthe surface layer 4, wherein a peak b₁ indicates a plane (110) as theclose-packed plane a₁, and a peak b₂ indicates a plane (211) as thesecondary slip plane a₂. It can be seen from FIG. 16 that Fe crystalsare present in the surface layer 4 and are oriented so that thesecondary slip plane a₂ lies in a plane parallel to the phantom plane Cextending along the slide surface 4a.

In this case, the greater the height of the peak b₂, and thus theintegrated strength of peak b₂, the greater the degree of orientation ofplane a₂ of the Fe crystals with respect to the phantom plane C. Thisresults in an increased percent area B of the secondary slip planes a₂in the slide surface 4a. The orientation degree is controlled by varyingthe conditions for the electroplating process. In FIG. 16, the percentarea B of the secondary slip planes a₂ in the slide surface 4a is 98%(B=98%). The structure of the Fe crystals in the slide surface 4a isshown by an electron photomicrograph (5,000× magnification) in FIG. 17.The inclination angle Θ of the secondary slip plane a₂ is in the rangeof 0°≦Θ≦20°.

FIG. 18A illustrates a comparison in hardness between the surface layersof the embodiment and a comparative example. FIG. 18B illustrates acomparison in the amount of wear between the surface layers of theembodiment and a comparative example. The surface layer of theembodiment has the slide surface in which the percent area B of thesecondary slip planes a₂ is 98%. In the surface layer of the comparativeexample, the crystal surfaces are oriented at random. A measurement ofthe amount of wear was conducted with a tip-on-disk testing machine. Thetest conditions were as follows: the load on the tip was set at 10 kgf;the material of the disk was a nitrid carbon steel material (S48Cmaterial); the speed of the revolutions was set at 0.5 m/sec; and thesliding distance was 1000 m.

As is apparent from FIGS. 18A and 18B, the surface layer of theembodiment exhibits a higher hardness as compared with the surface layerof the comparative example. As a result, the surface layer of theembodiment exhibits a superior wear resistance.

FIG. 19A illustrates a comparison in the density of cracks between thesurface layers of the embodiment, a comparative example and areferential example. FIG. 19B illustrates a comparison in the strengthbetween the surface layers of the embodiment and the comparativeexample. The surface layers of the embodiment and the comparativeexample are the same as those in FIGS. 18A and 18B. The surface layer ofthe referential example is one in which the percent area A of theclose-packed planes a₁ and thus of the planes (110) in the slide surfaceis 70% and the percent area B of the secondary slip planes a₂ is 30%.

The strength values were measured by a tension test under the followingconditions. FIG. 20 shows a test piece 8 with an entire length L₁ =50mm; a width W₁ at opposite ends=10.5 mm; a length L₂ betweenshoulders=32 mm; a length L₃ of a constant width portion=18 mm; a widthW₂ of the constant width portion=6 mm; and a thickness of 20 μm. Thefoil-formed test piece 8 was obtained by the process of first forming atest piece of the same structure as of the surface layer 4 by subjectinga stainless plate of the same dimension as of the test to anelectroplating process, and then separating the test piece 8 from thestainless plate. The tensile load rate was 20 mm/min under roomtemperature.

As is apparent from FIGS. 19A and 19B, the surface layer of theembodiment exhibits an extremely low value in the density of crackscompared to the surface layer of the comparative example. However, thesurface layer of the embodiment is superior to the surface layer of thecomparative example in strength. The superior strength is achieved bynot only the low density of cracks, but also the high hardness.

It should be noted from FIG. 19A that the density of cracks becomeshigher in the surface layer of the referential example due to anincrease in the orientation degree of the plane (110).

FIG. 21 is a X-ray diffraction pattern diagram for the Fe crystals inthe surface layer 4 of another example, wherein a peak b₁ indicates aplane (110) as the close-packed plane a₁, and a peak b₂ indicates aplane (211) as the secondary slip plane a₂. In this case, the percentarea B of the secondary slip plane a₂ in the slide surface 4a is 53%(B=53%). The Fe crystal structure in the slide surface 4a is shown by anelectron photomicrograph (5,000× magnification) in FIG. 22. Theinclination angle Θ of the secondary slip plane a₂ is in the range of0°≦Θ≦20°.

It should be noted that the improved technology of this invention in theabove-described second embodiment is not limited to the above-describedpiston, but also is applicable to other slide members such as an intakeor an exhaust valve of an internal combustion engine provided with asurface layer on a stem portion, a rocker shaft for an internalcombustion engine provided with a surface layer on a portion to besupported, and a cam shaft for an internal combustion engine providedwith a surface layer on a journal portion.

FIGS. 23 to 33 illustrate a third embodiment of the present invention.

Referring to FIGS. 23 and 24, a slide bearing 9 as a slide member isapplicable to a journal portion of a crankshaft in an engine, anenlarged end of a connecting rod or the like, and is comprised of afirst half 9₁ and a second half 9₂. The halves 9₁ and 9₂ have the sameconfiguration and each includes: a backing 10; a lining layer 11 formedon an inner peripheral surface of the backing 10; and a surface layer 4formed on a surface of the lining layer 11 and having a slide surface 4ain contact with a mating member 12. Optionally, a Cu plated layer may beprovided between the backing 10 and the lining layer 11, and an Niplated barrier layer may be provided between the lining layer 11 and thesurface layer 4.

The backing 10 is formed from a rolled steel plate. The thickness of thebacking 10 depends upon the thickness set for the slide bearing 9. Thelining layer 11 is formed from copper, copper based alloy, aluminum,aluminum based alloy, etc. The thickness of the lining layer 11 is inthe range of 50 to 500 μm and normally on the order of 300 μm. Thesurface layer 4 is formed from an aggregate of crystals of a Pb alloy.The thickness of the surface layer 4 is set in the range of 5 to 50 μmand normally on the order of 20 μm.

The Pb alloy forming the surface layer 4 contains 80 to 90% by weight ofPb and 3 to 20% weight of Sn. If necessary, the Pb alloy may contain atmost 10% by weight of at least one element selected from the groupconsisting of Cu, In, Ag, Tl, Nb, Sb, Ni, Cd, Te, Bi, Mn, Ca and Ba.

Cu, Ni and Mn have a function to increase the hardness of the surfacelayer 4. However, when the content of Cu, Ni and/or Mn exceeds 10% byweight, the resulting surface layer has an excessively high hardness,which will resulted in a reduced initial conformability. When Cu or thelike is added, it is desirable to control the Cu content such that thehardness Hmv of the resulting surface layer 4 is in the range of 15 to25.

Each of In, Ag, Tl, Nb, Sb, Cd, Te, Bi, Ca and Ba has a function tosoften the surface layer 4 to improve an initial conformability. Howeverwhen the content of such elements exceeds 10% by weight, the resultingsurface layer 4 has a reduced strength. When In or the like is added, itis desirable to control the In content such that the hardness Hmv of theresulting surface layer 4 is in the range of 8 to 15.

The surface layer 4 is formed by an electroplating process, wherein aplating solution used is a borofluoride based plating solutioncontaining 40 to 180 g/liter of Pb2+, 1.5 to 35 g/liter of Sn²⁺ andoptionally, at most 15 g/liter of Cu²⁺ together with an additive. Theadditive which may be used an organic additive and includes at least oneselected form the group consisting of a quinone based compound such ashydroquinone, catechol, etc., an amino acid based compound such asgelatin, peptone, etc., and an aldehyde such as benzaldehyde, vanillin.The added amount of the organic additives is set in the range of 1.5 to18 g/liter in total. Optionally, borofluoric acid and/or boric acid maybe added to the plating solution to control the electrical resistanceduring energization. The temperature of the plating solution is set inthe range of 5° to 35° C., and the cathode current density is set in therange of 3 to 15 A/dm².

The surface layer 4 has first oriented crystals with a plane (h00) ofhigh atomic density directed so as to form the slide surface 4a. Thefirst oriented crystals have a function to improve the slidingcharacteristic of the surface layer 4. The surface layer 4 may have, inaddition to the first oriented crystals, second oriented crystals withplanes (111) and (222) directed toward the slide surface.

In Pb alloy crystals, the plane (h00) and the plane (111) including(222) have a relationship such that as one of the planes (h00) and (111)increases, the other of the planes decreases. Accordingly, except in asurface layer 4 comprised of only the first oriented crystals, the firstoriented crystals should be considered in correlation with the secondoriented crystals.

In view of the above point, the presence rate of the first orientedcrystals in the surface layer 4 is set in the following manner:

Where the integrated strength of the first oriented crystals having theplane (h00) directed toward the slide surface 4a is represented by I(a),and the integrated strength of the second oriented crystals with theplanes (111) and (222) directed toward the slide surface 4a isrepresented by I(b), under application of an X-ray diffractometry to thesurface layer 4, the following relation is established:0.6≦I(a)/ΣI(ab)≦1.0 wherein ΣI(ab)=I(a)+I(b); I(b)=0 is included; andI(a)/ΣI(ab) represents the presence rate R₁ of the first orientedcrystals.

As shown in FIGS. 25 and 26, the first oriented crystals 13₁ with theplane (h00) directed toward the slide surface are columner crystalsextending from the lining layer 11 and having a quadrangularpyramid-shaped tip end 14 for forming the slide surface 4a incooperation.

If the presence rate R₁ of the first oriented crystals 13₁ is set in theabove-described manner, the apexes 14a of the quadrangularpyramid-shaped tip ends 14 are caused to be preferentially worn outwhereby the initial conformability of the surface layer 4 is improved.In addition, the surface area of the slide surface 4a can be enlarged bythe quadrangular pyramid-shaped tip ends 14, so that the surface layer 4has a sufficient oil retention property. This enhances the seizureresistance of the surface layer 4.

Because the first oriented crystal 13, has a face-centered cubicstructure due to the orientation of the plane (h00), the atomic densityincreases in the direction of the orientation. This provides the surfacelayer 4 with a high hardness and a high oil retention property, therebyimproving the wear resistance of the surface layer. In FIGS. 25 and 26,the reference numeral 13₂ represents second oriented crystals which aregranular.

In order to provide an excellent sliding characteristic as describedabove, the inclination of the first oriented crystals 13₁ should beconsidered.

Referring to FIG. 27, if a phantom plane C extending along the slidesurface 4a is defined on the side of a base surface of the quadrangularpyramid-shaped tip end 14, and an inclination angle defined by astraight line e passing through the apex 14a of the quadrangularpyramid-shaped tip end 14 and a central portion 14b of the base surfaceand by a referential line f extending perpendicular to the phantom planeC through the central portion 14b is defined as Θ, the inclination angleΘ of the first oriented crystals 13₁ is set in the range of 0°≦Θ≦30°.When the inclination angle Θ becomes larger than 30° (Θ>30°), the oilretention property of the surface layer 4 and the preferential wearingof the apexes 14a are reduced thereby to deteriorate the seizureresistance and wear resistance of the surface layer 4.

Preferred examples will now be described.

A lining layer 3 of a Cu alloy was subjected to an electroplatingprocess to form thereon a surface layer 4 comprised of an aggregate ofPb alloy crystals.

The conditions for the electoplating process were as follows: theplating solution was a boro-fluoride plating solution containing 100g/liter of Pb²⁺, 10 g/liter of Sn²⁺ and 3 g/liter of Cu²⁺ ; the additivewas an organic additive; the temperature of the plating solution was 25°C.; and the current density was 8 A/dm².

FIG. 28 is a X-ray diffraction pattern diagram for the Pb crystals inthe surface layer 4, wherein a peak b₄ indicates a plane (200), and apeak b₅ indicates a plane (400). Both of the planes (200) and (400)belong to the plane (h00). It is confirmed from FIG. 28 that the surfacelayer 4 is comprised of only the first oriented crystals 13₁. In thiscase, the total integrated strength ΣI(ab) is 679,996 (ΣI(ab)=679,996)with the proviso that I(b)=0. The value is equal to the integratedstrength I (a) of the first oriented crystals 13₁. Therefore thepresence rate R₁ of the first oriented crystals 13₁ is equal to 1.0 (R₁=1.0).

FIG. 29 is an electron photomicrograph (10,000× magnification) showingthe structure of Pb alloy crystals in the slide surface 4a. FIG. 30 isan electron photomicrograph (5,000× magnification) showing the structureof Pb alloy crystals at a longitudinal section of the surface layer 4.It can be seen from FIGS. 29 and 30 that the surface layer 4 iscomprised of the first oriented crystals 13₁ namely the columnarcrystals and the slide surface 4a is formed of quadrangularpyramid-shaped tip ends 14. The inclination angle Θ of the firstoriented crystals 13₁ is in the range of 0°≦Θ≦10°. The Pb alloy contains8% by weight of Sn and 2% by weight of Cu.

FIG. 31 is an electron photomicrograph (10,000× magnification) showingthe structure of Pb alloy crystals in another slide surface 4a. Secondoriented crystals 13₂ of granular share are also observed from FIG. 31in addition to the quadrangular pyramid-shaped tip ends 14.

In FIG. 31, the integrated strength I(a) of the first oriented crystals13₁ is 37,172 (I(a)=37,172) and the integrated strength I(b) of thesecond oriented crystals 13₂ is 24,781 (I(b)=24,781). Therefore thepresence rate R₁ of the first oriented crystals 13₁ becomes 0.6 (R₁=0.6). The inclination angle Θ of the first oriented crystals 13₁ is inthe range of 0°≦Θ≦10°.

FIG. 32 illustrates the relationship between the presence rate R₁ of thefirst oriented crystals 13₁ and the surface pressure when the seizureoccurs for surface layers 4 of various slide bearings 9. In FIG. 32, theline g₁ represents the relationship in a case where the inclinationangle Θ of the first oriented crystals 13₁ is in the range of 0°≦Θ≦10°,the line g₃ represents the relationship in a case where the inclinationangle Θ of the first oriented crystals 13₁ is in the range of 0°≦Θ≦20°,and the line g₃ represents the relationship in a case where theinclination angle Θ of the first oriented crystals 13₁ is in the rangeof 0°≦Θ≦+°.

The seizure test was carried out by bringing each of the slide bearings9 into sliding contact with a rotary shaft and gradually increasing theload applied to the slide bearings 9.

The test conditions were as follows: the material of the rotary shaftwas a nitrided JIS S48C material; the speed of rotation of the rotaryshaft was 6,000 rpm; the oil supply temperature was 120° C.; the oilsupply pressure was 3 kg/cm² ; and the applied load was 1 kg/sec.

As is apparent from FIG. 32, the seizure resistance of the surface layer4 can be improved by setting the presence rate R₁ of the first orientedcrystals 13₁ at a level equal to or more than 0.6 (R₁ ≧0.6). Apreferable range of the presence rate R₁ of the first oriented crystals13, is 0.8≦R₁ ≦1.0. It should be noted that the most excellent seizureresistance is obtained when R₁ =1.0.

In the surface layer 4, third oriented crystals, namely Pb metalcrystals with a crystal face other than of planes (h00), (111) and (222)being directed toward the slide surface, may be precipitated in somecases. The crystal face includes planes (220), (311) , (331) and (420).The third oriented crystals adversely affect the seizure resistance ofthe surface layer and hence, it is necessary to suppress the presencerate of the third oriented crystals.

In view of this problem, the presence rate of the third orientedcrystals in the surface layer is set in the following manner:

Where the integrated strength of the first oriented crystals with theplane (h00) directed toward the slide surface 4a is represented by, I(a), the integrated strength of the second oriented crystals with theplanes (111) and (222) directed toward the slide surface 4a isrepresented by I(b) and the integrated strength of the third orientedcrystals with planes other than the planes (h00), (111) and (222)directed toward the slide surface 4a is represented by I(c), underapplication of an X-ray diffractometry to the surface layer 4, thefollowing relation is established:

    I(c)/ΣI(abc)≦0.2

wherein ΣI(abc)=I(a)+I(b)+I(c); 1(b)=0 is included; and I(c)/ΣI(abc)represents the presence rate R₂ of the third oriented crystals.

FIG. 33 illustrates the relationship between the presence rate R₂ of thethird oriented crystals and the surface pressure at the generation ofseizure for the surface layers 4 of various slide bearings 9. In FIG.33, the line h₁ represents the relationship in a case where the presencerate R₁ of the first oriented crystals 13₁ is 1.0 (R₁ =1.0) and thusI(b)=0 and the surface layer 4 is comprised of the first and thirdoriented crystals. The line h₂ represents the relationship in a casewhere the presence rate R₁ of the first oriented crystals 13₁ is 0.8 (R₁=0.8) and the surface layer 4 is comprised of the first, second andthird oriented crystals. The seizure test was carried out in the samemanner and under the same conditions as those described above.

As is apparent from FIG. 33, the seizure resistance can be improved bysetting the presence rate R₂ of the third oriented crystals at a levelequal to or less than 0.2 (R₂ ≦0.2). The presence rate R₂ of the thirdoriented crystals is preferably set in the range of R₂ ≦0.1. It is to benoted that R₂ ≦0 corresponds to the case where no third orientedcrystals exist in the surface layer 4.

The optimum state of the surface layer 4 is achieved when theinclination angle e of the first oriented crystals 13₁ is in the rangeof 0°≦Θ≦10° and when the presence rate R₁ of the first oriented crystals13, is determined by the following expression:

    R.sub.1 =I(a)/ΣI(abc)≧0.8

It should be noted that the third embodiment of the present invention isalso applicable to slide members other than the described slide bearing.

What is claimed is:
 1. A slide member comprising a surface layer havinga slide surface for a mating member, wherein the surface layer is formedof an aggregate of crystals of a Pb alloy, and under application of anX-ray diffractometry to the surface layer, when I(a) represents anintegrated strength of first oriented crystals with a (h00) plane byMiller indices thereof being directed toward the slide surface, and I(b)represents an integrated strength of second oriented crystals with (111)and (222) planes by Miller indices thereof being directed toward theslide surface, the following expression being established:

    0.6≦I(a)/ΣI(ab)≦1.0

wherein ΣI(ab)=I(a)+I(b), and I(b)=0 is included.
 2. A slide membercomprising a surface layer having a slide surface for a mating member,wherein the surface layer is formed of an aggregate of crystals of a Pballoy, said crystal including first, second and third oriented crystals,and under application of an X-ray diffractometry to the surface layer,when I(a) represents an integrated strength of the first orientedcrystals with a (h00) plane by Miller indices thereof being directedtoward the slide surface, I(b) represents an integrated strength of thesecond oriented crystals with (111) and (222) planes by Miller indicesthereof being directed toward the slide surface, and I(c) represents anintegrated strength of the third oriented crystals with planes otherthan the (h00), (111) and (222) planes by Miller indices thereof beingdirected toward the slide surface, the following expression beingestablished:

    I(c)/ΣI(abc)≦0.2

wherein ΣI(abc)=I(a)+I(b)+I(c), and I(b)=0 is included.
 3. A slidemember according to claim 1 or 2 wherein an inclination angle Θ of anaxis of each the first oriented crystals relative to a lineperpendicular to a plane on which the slide surface lies is in a rangeof 0°≦Θ≦30°.